LG 3828W5S3899 Service Manual

MICROWAVE OVEN

SERVICE MANUAL

MODEL: MD-0983FTL

CAUTION

BEFORE SERVICING THE UNIT, READ THE SAFETY PRECAUTIONS IN THIS MANUAL.

Website: http://biz.lgservice.com

P/NO : 3828W5S3899

July, 2004

Printed in Korea

This device is to be serviced only by properly qualified service personnel. Consult the service manual for proper service procedures to assure continued safety operation and for precautions to be taken to avoid possible exposure to excessive microwave energy.

PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE EXPOSURE TO EXCESSIVE MICROWAVE ENERGY

A) Do not operate or allow the oven to be operated with the door open. B) Make the following safety checks on all ovens to be serviced before activating the magnetron or other

microwave source, and make repairs as necessary; (1) interlock operation, (2) proper door closing, (3) seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and latches, (5) evidence of dropping or abuse.

C) Before turning on microwave power for any service test or inspection within the microwave generating

compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity, and connections.

D) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave generation

and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual before the oven is released to the owner.

E) A microwave leakage check to verify compliance with the Federal Performance Standard should be

performed on each oven prior to release to the owner.

SAFETY PRECAUTIONS

CAUTION

MICROWAVE RADIATION

DO NOT BECOME EXPOSED TO RADIATION FROM THE MICROWAVE GENERATOR OR OTHER PARTS CONDUCTING MICROWAVE ENERGY.

(Page)

SAFETY PRECAUTIONS

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Inside front cover

SPECIFICATIONS

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1-1

CAUTIONS

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2-1

INSTALLATIONS

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3-1

OPERATING INSTRUCTIONS

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4-1

FEATURES

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4-1

CONTROL PANEL

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4-1

OPERATING SEQUENCE

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4-2

SCHEMATIC DIAGRAM

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4-3

CIRCUIT DESCRIPTION

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4-4

SERVICE INFORMATION

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5-1

TOOLS AND MEASURING INSTRUMENTS

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5-1

MICROWAVE LEAKAGE TEST

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5-1

MEASUREMENT OF MICROWAVE POWER OUTPUT

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5-3

DISASSEMBLY AND ADJUSTMENT

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5-3

INTERLOCK CONTINUITY TEST

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5-7

COMPONENT TEST PROCEDURE

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5-8

TROUBLESHOOTING

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5-12

EXPLODED VIEW

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6-1

REPLACEMENT PARTS LIST

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7-1

CONTENTS

This microwave oven is designed for household use only.

It is not recommended for commercial purposes.

DESCRIPTION

MD-0983FTL

120 Volts AC 60 Hz

Single phase, 3 wire grounded

Microwave 1350W

Toast 800W

900 Watts full microwave power (IEC60705)

2450 MHz

2M214 - 39F

0 ~ 99 min

541 (W) x 302 (H) x 439 (D) mm

342 (W) x 233 (H) x 347 (D) mm

16.5 kg (approx.)

18 kg (approx.)

Microwave Power for Variable Cooking

Power level

MAX ................................................ Full power throughout the cooking time

MED.-HIGH .................................... approx. 80% of Full power

MEDIUM ......................................... approx. 60% of Full power

DEFROST ...................................... approx. 40% of Full power

LOW/WARM ................................... approx. 20% of Full power

TOAST, COMBI

Owner's manual

Glass turntable

Rotating ring

1-1

ITEM

MODEL

Power Requirement

Power Output

Microwave Frequency

Magnetron

Timer

Outside Dimensions

Cavity Dimensions

Net Weight

Shipping weight

Control Complement

Nameplate Location

Accessories

SPECIFICATIONS

Back side

• DO NOT operate on a 2-wire extension cord during repair and use.

• NEVER TOUCH any oven components or wiring during operation.

• BEFORE TOUCHING any parts of the oven, always remove the power plug from the outlet.

• For about 30 seconds after the oven stops, an electric charge remains in the high voltage capacitor. When replacing or checking, you must discharge the high voltage capacitor by shorting across the two terminals with an insulated screwdriver.

• Remove your watches whenever working close to or replacing the Magnetron.

• NEVER operate the oven with no load.

• NEVER injure the door seal and front plate of the oven cavity.

• NEVER put iron tools on the magnetron.

• NEVER put anything into the latch hole and the interlock switches area.

• Proper operation of the microwave oven requires that the magnetron be assembled to the waveguide and cavity. Never operate the magnetron unless it is properly installed.

• Be sure that the magnetron gasket is properly installed around the dome of the tube whenever installing the magnetron.

2-1

CAUTIONS

Unlike other appliances, the microwave oven is high-voltage and high-current equipment. Though it is free from danger in ordinary use, extreme care should be taken during repair.

THE OVEN IS TO BE SERVICED ONLY BY PROPERLY QUALIFIED SERVICE PERSONNEL.

MICROWAVE RADIATION

Personnel should not be exposed to the microwave energy which may radiate from the magnetron or other microwave generating device if it is improperly used or connection. All input and output microwave connections, waveguide, flange and gasket must be secure never operate the device without a microwave energy absorbing load attached. Never look into an open waveguide or antenna while the device is energized.

Gasket

ANTENNA

COOLING FIN

MAGNETRON CHASSIS GROUND

FILAMENT TERMINALS

MAGNETRON

INSTALLATIONS

3-1

INSTALLING

1. Empty the microwave oven and clean inside it with a soft, damp cloth. Check for damage such as misaligned door, damage around the door or dents inside the cavity or on the exterior.

2. Put the oven on a counter, table, or shelf that is strong enough to hold the oven and the food and utensils you put in it. (The control panel side of the oven is the heavy side. Use care when handling.)

3. Do not block the vent and the air intake openings. Blocking vent or air intake openings can cause damage to the oven and poor cooking results. Make sure the microwave oven legs are in place to ensure proper air flow.

4. The oven should not be installed in any area where heat and steam are generated, because they may damage the electronic or mechanical parts of the unit. Do not install the oven next to a conventional surface unit or above a conventional wall oven.

5. Use microwave oven in an ambient temperature less than 104°F(40°C).

6. Place the microwave oven on a sturdy and flat surface at least 10 cm(4 inches) from the wall.

7. Place the microwave oven as far away as possible from TV, RADIO, COMPUTER, etc., to prevent interference.

8. Do not touch the front glass during or after cooking of the Grill and Combination mode. This glass is very hot during heater operating.

9. Do not operate the oven at microwave and combination mode with Grill rack placed in the cavity when the oven is empty.

EARTHING INSTRUCTIONS

This microwave oven is designed to be used in a fully earthed condition. It is imperative, therefore, to make sure it is properly earthed before servicing

WARNINGTHIS APPLIANCE MUST BE EARTHED

IMPORTANT

As the colors of the wires in the mains lead of this appliance may not correspond with the colored markings identifying the terminals in your plug, proceed as follows.

The wire which is colored green-and-yellow must be connected to the terminal in the plug which is marked with the letter E or by the earth symbol ( ) or colored green or green-and-yellow.

The wire which is colored blue must be connected to the terminal in the plug which is marked with the letter N or colored black.

The wire which is colored brown must be connected to the terminal in the plug which is marked with the letter L or colored red.

BEFORE YOU BEGIN, READ THE FOLLOWING INSTRUCTIONS COMPLETELY AND CAREFULLY.

The wires in this mains lead are colored in accordance with the following code:

Green-and-yellow: Earth Blue: Neutral Brown: Live

10cm

4-1

OPERATING INSTRUCTIONS

FEATURES

CONTROL PANEL

MICROWAVE CONTROL AREA

1. DISPLAY. The Display includes a clock and indicators that tell

you time of day, cooking time settings, and cooking functions selected.

2. AUTO COOK. Touch this button and turn the dial knob to select

programmed food items.

3. AUTO DEFROST. This button is an accurate defrosting method

for frozen meat, poultry, fish up to 6.0 lbs. and Bread up to 1.0 lbs. Touch this button and turn the dial knob to defrost.

4. POPCORN. Touch this button to pop a bag of microwave

popcorn without entering a cook power or time.

5. CLOCK. Touch this button to set the time of day.

6. KITCHEN TIMER. Touch this button to use your microwave oven

as a kitchen timer.

7. COOK TIME. Touch this button to set a cooking time.

8. DIAL KNOB. Turn the dial knob to set clock, kitchen timer, cook

time, power level, food quantity and toast/bagel baking level.

9. EZ ON. Touch this button to cook at 100% cook power for 1 minute to 99 minutes 59 seconds.

10. STOP/CLEAR. Touch this button to stop the oven or clear

entries.

11. POWER. Touch this button to set a cooking power.

12. START. Touch this button to start all entries (except Auto Cook,

Popcorn and Ez on function which start automatically) and to turn Child Lock on or off.

TOASTER CONTROL AREA

1. Toast. Touch this button and turn the dial knob to bake toast

bread.

2. Bagel. Touch this button and turn the dial knob to bake bagel.

3. Stop/Clear. Touch this button to stop the toaster or clear

entries.

4. Start. Touch this button to start the toasting process.

5. Indicator Light. When operating toaster with door closed, this

will be illuminated. If you open the door during toasting, this will blink.

Easy-Clean

Oven Cavity

See-Through Door

Safety Interlock System

Rotating Ring

Glass Turntable

Slots

Microwave Oven Toaster

Control Panel

Toaster Indicator Light

Toaster Door

Crumb Tray

4-2

OPERATING SEQUENCE

The following is a description of component functions during oven operation.

1. SETTING THE CLOCK

NOTE: You can set 12 hour clock or 24 hour clock

optionally.

2. CANCEL FUNCTION

Touch the Parar/Borrar pad whenever you need to cancel an entry or a function currently in use. The display will either return to the last item entered or to the clock.

3. QUICK START

4. MICROWAVE COOKING

5. TOAST

6. TWO STAGE COOKING

7. AUTO WEIGHT DEFROST

8. AUTO COOK

9. CHILD LOCK

This oven has a CHILD LOCK feature.

• TO SET CHILD LOCK

• Touch the Parar/Borrar pad

• Touch INICIO pad L appear in

the display.

• TO CANCEL CHILD LOCK

• Touch the Parar/Borrar pad

• Touch INICIO pad L disappears.

Parar/

Borrar

Reloj InicioNumber

Parar/ Borrar

Number Potencia Number Inicio

Parar/ Borrar

Time Number Potencia

Number Time Number Potencia

Number Inicio

Parar/Borrar Inicio

Parar/ Borrar

Desired

defrost

category

Inicio

Desired cooking

weight

Parar/

Borrar

Power

Level

Inicio

SCHEMATIC DIAGRAM

4-3

CIRCUIT DESCRIPTION

GENERAL DETAILS

• The low voltage transformer supplies the necessary voltage to the micom controller when power cord is plugged in.

• When the door is closed, the primary switch is ON, the secondary switch is ON, and the monitor switch opens (contact COM and NO).

WHEN SELECTING COOKING POWER LEVEL AND TIME

• The micom controller memorizes the function you set.

• The time you set appears in the display window.

• Each indicator light turns on to indicate that the stage

has been set.

WHEN TOUCHING THE START PAD

• The coil of the relay is energized by the micom controller.

• Power input is supplied to the high voltage transformer through the fuse to the primary switch and relay 3.

• Turntable rotates.

• The fan motor rotates and cools the magnetron by

blowing the air (coming from the intake on the baseplate).

• The air is also directed into the oven to exhaust the vapor in the oven through the upper plate.

• Cooking time starts counting down.

• 3.2 volts AC is generated from the filament winding of

the high voltage transformer. This 3.2 volts is applied to the magnetron to heat the magnetron filament through two noise-preventing choke coils.

• A high voltage of approximately 2100 volts AC is generated in the secondary of the high voltage transformer which is increased by the action of the high voltage diode and charging of the high voltage capacitor.

• The negative 4000 Volts DC is applied to the filament of the magnetron.

WHEN THE OVEN IS SET AT ANY LEVEL EXCEPT MAXIMUM.

• The micom controller controls the ON-OFF time of relay 3 by the applied signal to vary the average output

power of microwave oven as POWER LEVEL.

(refer to page 1-1)

• One complete cycle of relay 3 is 22 seconds.

WHEN THE DOOR IS OPENED DURING COOKING

• Both the primary switch and relay 3 are cut off primary winding voltage of the high voltage transformer.

• ON-OFF of relay 3 is coupled electrically with opening and closing of the secondary switch.

• When the door is opened, the secondary switch is opened and when the door is closed, the secondary switch is closed.

• The cooking time stops counting down.

• Relay stops functioning.

• As the door is opened, if the contact of primary switch

and relay 3 fails to open, the fuse opens due to the large current surge caused by the monitor switch activation, which in turn stops magnetron oscillation.

WHEN TOUCHING THE START KEY WITH THE GRILL COOKING FUNCTION SELECTED

• The contacts of the primary switch and the secondary switch close the circuit.

• A.C. voltage is applied to the toast heater through toast thermostat as shown by the solid line.

• Turntable rotates.

• The fan motor rotates.

• The air is also directed into the oven to exhaust the

vapor in the oven through the base plate and upper plate.

FUSE

H.V.

TRANS-

FORMER

RELAY 3

MICOM CONTROLLER

SECONDARY SWITCH

PRIMARY

SWITCH

MONITOR

SWITCH

4-4

PRIMARY

FUSE

SWITCH

MONITOR

SWITCH

H.V.

TRANS-

FORMER

RELAY 3

MICOM CONTROLLER

SECONDARY SWITCH

G -Y

RELAY 4

TOAST

HEATER

TOAST

THERMOSTAT

CAUTIONS

• Be sure to check microwave leakage prior to servicing the oven if the oven is operative prior to servicing.

• The service personnel should inform the manufacture importer, or assembler of any certified oven unit found to have a microwave emission level in excess of 5 mW/cm2and should

repair any unit found to have excessive emission levels at no cost to the owner and should ascertain the cause of the excessive leakage. The service personnel should instruct the owner not to use the unit until the oven has been brought into compliance.

• If the oven operates with the door open, the service personnel should:

- Tell the user not to operate the oven.

- Contact the manufacturer.

• The service personnel should check all surface and vent openings for microwave leakage.

• Check for microwave leakage after every servicing. The power density of the microwave radiation leakage emitted by the microwave oven should not exceed 4 mW/cm2. Always start measuring of an unknown field to assure safety for operating personnel from radiation leakage.

MEASURING MICROWAVE ENERGY LEAKAGE

• Pour 275±15cc of 20±5°C(68±9°F) water in a beaker which is graduated to 600 cc, and place the beaker on the center of the turntable.

• Set the energy leakage monitor to 2,450 MHz and use it following the manufacturer's recommended test procedure to assure correct result.

• When measuring the leakage, always use the 2 inch (5cm) spacer supplied with the probe.

• Operate the oven at its maximum output.

• Measure the microwave radiation using and electromagnetic radiation monitor by holding the probe perpendicular to the surface being measured

Move probe along shaded area

Probe scanning speed Less than 2.5 cm/sec (1in/sec)

5-1

SERVICE INFORMATION

TOOLS AND MEASURING INSTRUMENTS

MICROWAVE LEAKAGE TEST

NECESSARY TOOLS

Tools normally used for TV servicing are sufficient. Standard tools are listed below.

• Diagonal pliers

• Long nose pliers

• Phillips screwdriver

• Flat blade screwdriver

• Wrench (size 5mm)

• Nutdriver (size 5mm)

• Adjustable wrench

• Soldering iron

• Solder

• Vinyl insulation tape

• Polishing cloth

NECESSARY MEASURING INSTRUMENTS

• TESTER(VOLTS-DC, AC., Ohmmeter)

• Microwave survey meter

- Holaday HI-1500 HI-1501

- Narda 8100 8200

• Inch scale

• 600 cc non conductive material beaker (glass or plastic),

inside diameter: approx. 8.5 cm(31/

2 in.)

• Cylindrical and made of borosilicate glass vessel. max. thickness: 3 mm outside diameter: approx. 190mm height: approx. 90mm

• Glass thermometer: 100°C or 212°F (1 deg scale)

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